Decolorizing and dewaxing petroleum lubricating oils



July 16, 1935. c. F. TEARS DECOLORIZING AI I D DEWAXING PETROLEUM LUBRICATING OILS Filed Jan. 27, 1934 1 Propane slvrdge Cold PM he Supply 7517K ENTOR INV CLAUDE F. TEARS A RNEY Patented July 16, 1935 UNITED STATES PATENT OFFICE DECOLORIZING AND DEWAXING PETRO- LEUM LUBRICATING OILS Claude F. Tears, Mountain Lakes, N. J., assignor to The Petroleum Processes Corporation, Wichita, Kans., a corporation of Kansas Application January 27, 1934, Serial No. 708,608

2 Claims. (Cl. 196-18) This invention relates to the removal of color the naphtha solution below the solidification and wax from lubricating oils and one of the point of the wax and settling the wax out of the important objects of the invention is to combine mixture as petrolatum in large settling tanks these two distinct operations in a single process. over long periods of chilling and settling.

5 In conventional refinery practice, the lubricat- In both centrifuge and cold settling methods, 5 ing oil fractions are usually divided into two the naphtha solution is distilled at relatively high portions, wax distillate forming the lighter portemperatures to remove the naphtha and recover tion and cylinder stock or steam refined stock, the lubricating oil fraction as a residual product. the heavier portion. In some instances, the total Both cold settling and centrifuge processes are lubricating oil fraction is handled as one in what ineiiiclent and expensive methods of wax remov- 10 is known as the long residuum operation. In a1, demanding excessive refrigeration for acceptboth methods, the various oil fractions are deable de-waxing, because of the long spread rewaxed and decolorized by separate processes. quired between the chilling temperature and the In the practice first outlined, the wax distilpour test obtained. Furthermore, the petrolatum late is usually chilled and pressed through high of bo pe s c a s a h p enta of 15 I pressure plate filters to remove the wax. This lubricating oil, ranging from 25% to 75%, deoperation is only partly effective, making it necpending upon the system employed and the pour essary to double press with lower temperature test of the oil finally produced. on the second pressing, to produce a light lubri- In addition to the conventional practices outeating oil of low pour test, e. g. 0 F. to 5 F. e tie-Waxing has been accomplished by (115- 0 After de-waxing, the wax distillate is fracsolving the lubricating oil stock in propane or tionated to gas oil and light and heavy neutral similar normally gaseous petroleum hydrocarbon oils. These neutral oils'are then usually decolat slightly elevated temperatures andunder suforized by fullers earth in percolation filters. fi i ntly i h p ssu t p t v nt n the The heavier cylinder stock or steam refined liquid state. This solution is cooled as by water. 25 stock portions of the first method or the so-called coolers and ex hangers and fina mp ratur relong residuum of the second method are usually duction to that required for crystallization of the de-waxed by centrifuging or cold settling. The wax is effected by evaporating part of the solvent decolorization of these stocks also is a separate under reduced pressures. The wax'and oil solustep, but usually performed before the de-waxtion are then separated by filtration through me- 30 ing. Such decolorization may be either by perchanical filters. This process requires careful colation or contact filtration. control of chilling rates and solvent ratios to In the percolation method, the heavy lubripromote h proper w x ryst l rowth that will eating oil is dissolved in light. naphtha. and permit filtration 0f the wax by mechanical filters.

pumped through percolation filters containing Decolorization has been accomplished by the 35 beds of fullers earth or other decolori'zing meuse of fullers earth or other decolorizing medium dium. with the oil in solution in liquid propane or the The contact method involves mixing fine fu1- like. This process is disclosed in the Tears pat lers earth, of 200 mesh or the like, or other deent appli i n Ser- N covering both 40 colorizing agent with the oil, usually in naphtha contact and percolation methods of filtration. 4 solution and usually at elevated temperatures, In the present invention, both decolorization In some instances, the clay is mixed with the and ole-waxing are effected in the same operation. oil and the mixture heated and then cooled be- In the present disclosure, this is accomplished by fore mixing with naphtha. The whole mixture is a combination of contact filtration and de-waxt passed through filter pr i whi h the ing in propane or solvent of like nature. De- 45 fine decolorizing medium is filtered out of the. colorizing clay is mixed in a p p Solution, solution. the mixture is chilled by flash evaporation, of part If the de-waxing is to be effected by centrifugof the propane and the wax thereby solidified is ing, the naphtha solution is chilled slowly under filtered out of the propane-oil solution, using the nued temperatures and chilling rates to prodecolorizing medium to assist the wax removal. 50 mote wax solidified as necessary to enable re- The wax-clay component is then washed with cold moval of the wax as petrolatum by centrifugal pr pane to free it of retained oil-propane soluforce and the cold mixture is then centrifuged to tion and warm propane is then used to melt and effect removal of the wax as the heavier portion. flush the wax out of the decolorizing clay. The

De-waxing by cold settling involves chilling oil-solvent and wax-solvent portions are sepa- 55 rately stabilized and stripped and the de-oiled and de-waxed decolorizing medium is removed from the system as a part of the clearing of the filter.

Various other novel features of the invention will appear as the specification proceeds and will be apparent from consideration of the accompanying drawing, which represents a flow sheet diagram of one practical method of carrying out the invention. This showing is primarily illustrative and is to be so considered, the claims defining the broad scope of the invention.

In the diagram, the lubricating oil stock which is to be decolorized and de-waxed is transferred from a storage tank I, to an agitator 2, by a pump 3. v

The agitator is indicated as of the mechanical mixer type and is shown equipped with heating coils 4, by which the oil may be brought up to a temperature best suited to the. removing of color.

In the present disclosure, the decolorizing clay is introduced at 5, into the oil, warmed and in course of agitation in the agitator, this being a desirable method of getting the necessary con--v tact of oil and clay for decolorization, but it is within the scope of the invention that the decolorizing-medium beintroduced in the system with the solvent or with the solvent-oil solution.

The warm oil-clay mixture is transferred. from the agitator by pump 6, to a mixer 1, and there it is combined with liquid propane or like solvent from storage tank 8, transferred to the mixer by pump 9.

To assure thorough mixing of clay, oil and propane, the mixture may then be passed through a heater l0.

With mixing and dissolving of the oil in the solvent properly accomplished, temperature reduction may be initiated as by passing the mixture through a suitable cooler indicated at H.

The mixing system, which may be considered as including the heater, and the cooler are all closed in to keep pressure sufficient to hold the propane or like solvent in the liquid state. This is effected in the illustration by a back pressure valve l2.

Final chilling suflicient for solidifying wax in the mixture is effected, in the present disclosure by expansion of the mixture into a flash chiller 13, the back pressure valve being set usually to effect a reduction to atmospheric pressure in this chiller. This reduction of pressure and evaporation of propane produces a lowering of temperatureto 45 F., the equilibrium temperature at atmospheric temperature. If higher temperature is permissible under the circumstances, the flash chiller is vented to correspondingly higher pressures.

To keep the wax and clay suspended in the mixture and prevent them from settling out in the flash chiller, there is provided in the illustration a perforated coil M, in the bottom of the chiller, which can be supplied with gaseous propane through line l5, from the top of the propane storage tank. This agitation also aids in the solidification and the separation of wax from the oil solution. The propane vaporreleased from the top of the flash chiller by valve I6, is saved and reused by passage through line l1, to compressor l8, condenser l9 and line 20, to liquid propane storage tank 8. Bailles 2|, in the chiller prevent entrainment of liquid with this vapor on, the way back to storage.

The chilled mixture of wax, decolorizing clay and oil-propane solution is taken from the bottom of the flash chiller and transferred by pump 22, to filters 23, 24, which usually through valve connections 25, 26, are alternated, one filtering while the other is being washed and cleaned.

These filters are of the pressure type, to hold the solvent in the liquid phase and in them, the decolorizing clay and solidified wax portions of the mixture are filtered out of the oil-propane solution, the clay and wax being retained on the filter plates and the oil-propane solution passing through, into the outer shells of the filters shown.

The decolorizing clay in mixture with the wax crystals forms a filter cake that will not mat or plug as does wax alone. Furthermore, the time required for formation of this cake is less, because of the clay present, reducing or eliminating the amount of oil that might require slopping because of high wax content.

The filtrate, the oil-propane solution, decolorized and de-waxed passes out through line 21, to oil stabilizer 28, where propane is distilled off under pressure and passes through line 29, to condenser l9 and thence through 20, to propane storage tank 8. The partially stripped oil discharges from the bottom of the stabilizer through line 30, to oil stripper 3|, where remaining traces of propane are distilled 01f under pressure due to suction of the compressor, this stripper being indicated as connected at the top by line 32, with the suction side of the compressor.

The wax and clay mixture on the filter plates is washed with cold propane to remove traces of oil, by operating pump 33, to force cold propane from tank 34, through valved connections 35, 36, to the filters, after cutting off the flash chiller connections at 25, 26.

The cold wash propane is prepared in the pres.- ent disclosure by expanding liquid propane from storage pressure, coming through line 31, to the compression line suction pressure, by means of expansion valve 38, opening into the cold storage tank 34. The head of this tank is shown connected with the compressor suction line l1, by a valved line 39, and baflle assemblies 40, are shown in this tank for preventing entrainment of liquid in the vapor passing off to the compressor.

This cold stored liquid propane is at approximately the same temperature as the mixture in the flash chiller. Washing the wax and clay on the filter plates with this cold propane removes traces of oil held in the filter cake. The wash liquor may be passed through the valved lines 21, to the oil stabilizer, where the propane can be distilled off and returned to storage and the oil be collected as a residue and stripped as above described.

After being washed of oil, the filter cake is washed with warm propane taken from storage by pump 4| and heated at 42, suihciently to melt and re-dissolve the wax in the wax-clay mixture, this heated propane being delivered into the filters through valved lines 43, 44.

The solution of wax and warm propane is taken 01f from the filters through valved lines 45, to wax stabilizer 43, where propane is distilled off under pressure, passing through lines 41, 29, to the propane condenser and storage and the wax passing off at the bottom at 48, to the wax stripper 49, from which propane passes off through- 50, 32, to suction side of the compressor.

The stripped lubricating oil decolorized and dewaxed is run down to storage at 5|, and wax freed of oil and decolorizing clay and stripped of solvent is run down to storage at 52.

The decolorizing clay, washed of oil and denuded of wax, may be removed from the filter, in the illustration, by taking the filter assembly out of the pressure shell and scraping the clay off the plates. Before opening the filters, the shells may be vented to the compressor suction through valve lines 53, 54, to remove propane from the filter cake. This leaves the clay substantially dry and easily removable. If desired, the clay may be washed With a color removing solvent, such as trichlorethylene, before or after removal from the filter, for re-use, but in view of the economies effected by the process, it may simply be discarded or put to other uses.

Filters of the edge or continuous types which efiect continuous removal of cake'and washing of the cake may be employed, with provision for pressure to keep the solvent liquid.

The effectiveness of the process may be indicated by way of a specific example, in which long range distillate of lubricating oil from Mid Continent crude having a viscosity of 400 seconds Saybolt at 100 F. was dewaxed and decolorized as described above, using an acid treated decolorizing clay in the proportion of lb. per gallon of charge, mixed at 110 F. and the flash chiller vented to atmospheric pressure. The finished oil had a color of 3 /2 N. P. A. and a pour test of l0 F. with no cloud showing at that temperature.

The process has all the advantages of a propane dewaxing process and those of a propane decolorizing operation and special advantages that neither of these possess, including that of a combination of all in one economical unit.

It will be apparent that the process is particularly well suited to handle long residuum or.

total lube distillates, because it can be operated so economically and because all grades of wax can be removed, the different wax structures in the several fractions of the oil being all handled without difficulty.

Higher yields of lubricating oils are obtained because of washing the oil from the wax with cold propane, while the wax is held on the filter plates. The presence of the decolorizing clay makes this possible and feasible because the filter cake does not mat as when filtering wax alone. For these same reasons, the wax produced has a higher melting point and a lower oil content.

The process requires no such close attention to solution ratios and chilling rates as in known propane dewaxing processes. Satisfactory operation, for example, is obtained using the flash chilling, with propane contents varying between 35% and 85%, after chilling.

The process is suited to the handling of short range wax distillates, that is, wax distillates which do not contain the large amounts of gas oil required in normal refinery practice for the control of crystal growth. This is because in the present process, the crystal growth is not so important and vital an item and is taken care of more readily because of the presence of the decolorizing clay.

While refrigeration by vaporization of the propane is practical and desirable, this is not essential as indirect chilling of the propane solution or a combination of indirect chilling and chilling by evaporation, may be employed.

Another important feature is that none of the decolorized and de-waxed oil need be subjected to temperatures above 200 F. or that required to remove the propane from the oil. The deleterious cosity, serving to increase the activity of the decolorizing medium. The effective usefulness or life of the clay is thus extended.

The presence of the decolorizing clay in the filter, in mixture with the wax crystals, minimizes the care, control and time required to produce a filterable wax mixture and because of the fact that the filter cake so formed does not mat, the propane-oil solution may be passed through at long maintained high filter rates.

The fact that wax crystal growth control is minimized makes it possible to carry on a continuous chilling operation, with rapid flash evaporation of the propane for refrigeration.

The presence of the decolorizing clay permits the removal of the wax at higher temperatures than would be possible without the clay, because with the clay the filter surface is made more effective for wax removal. This has the ultimate effect of lessening the amount of refrigeration required to produce an oil having a desired low pour test.

The combination of the two decolorizing and dewaxing operations as disclosed, enables the utilization of much common equipment and avoids the expense of duplicating various units. This is particularly true of the filtration units which serve the dual purpose of separating the decolorizing medium and the wax from the propane-oil solution. 4

Also in the invention, the oil-solvent ratio is not critical and need not be kept constant. The propane vappr introduced for agitating and keeping the decolorizing clay and wax in suspension in the flash chiller may be controlled as a means for compensating for the amount evaporated or for varying or otherwise governing the oil-solvent re. 10.

While propane has been given as an example of a solvent suitable for the carrying out of the process, it will be appreciated that other solvents of like character might be substituted and this expression, as well as others employed herein are therefore to be construed in a descriptive rather than in a limiting sense, except possibly as limitations may be imposed by state of the prior art.

What is claimed is:

1. The herein disclosed process of decolorizing and dewaxing petroleum lubricating oils in one continuous operation which comprises mixing comminuted adsorbent decolorizing medium with the lubricating oil, mixing normally gaseous liquefied hydrocarbon solvent with said mixture of lubricating oil and decolorizing medium, heating the whole mixture to effect substantially complete solution of oil and wax in the solvent, cooling to remove added heat, flash vaporizing suflicient of the normally gaseous liquefied hydrocarbon to chill the remaining mixture to wax solidification temperature, filtering the oil-solvent component from the wax-decolorizing medium component and separately recovering the solvent from the oilsolvent component and the wax-decolorizing medium component.

2. The herein disclosed. process of decolorizing and dewaxing petroleum lubricating oils in one continuous operation which comprises mixing comminuted adsorbent decolorizing medium with the lubricating oil, mixing normally gaseous liquefied hydrocarbon solvent with said mixture of lubricating oil and decolorizing medium, heating the whole mixture to efiect substantially complete solution of oil and wax in the solvent, cooling to remove added heat, flash vaporizing sufficient of the normallyv gaseous liquefied hydrocarbon to chill the remaining mixture to wax solidification temperature, filtering the oil-solvent component from the wax-decolorizing medium component, washing the wax-decolorizing medium component retained in the filter with fresh cold solvent to remove traces of oil, dissolving the wax from the in situ with fresh warm solvent, drying the filtered decolorizing medium by reducing the pressure onthe filter thereby vaporizing the normally gaseous liquefied hydrocarbon solvent therein and separately recovering the solvent from the oil and wax components.

CLAUDE F. TEARS. 

